This invention relates to a piezoelectric diaphragm and a piezoelectric speaker to be used for a portable electronic device, such as a mobile communication terminal.
Conventionally, receivers or speakers used in portable electronic devices are typically of dynamic type or piezoelectric type. In recent years, especially for mobile telephone terminals, a large-area LCD (liquid crystal display) to display information such as image etc. has been desired increasingly.
With such enlargement of LCD area, a reduction in the area of a diaphragm for a receiver or speaker has been required. However, if the area of diaphragm is reduced to give a large-area LCD, the efficiency of electrical-acoustical conversion reduces and therefore the sound pressure reduces.
Japanese patent application laid-open No.4-70100 (1992) discloses a piezoelectric transparent speaker that can be made lighter and thinner than a dynamic type speaker and is provided with a transparent diaphragm, which can expand the range of use.
However, in case of a bimorph that piezoelectric ceramic for piezoelectric speaker is attached to both sides of a metallic diaphragm, the manufacturing cost increases since lead wires for electrode need to be led out from the two sides.
Also, in case of the transparent piezoelectric diaphragm that is attached to the front face of a display device such as a LCD etc, the manufacturing cost increases since lead wires for electrode also have to be formed with transparent conductive material.
Accordingly, it is an object of the invention to provide a piezoelectric diaphragm and a piezoelectric speaker that can lend a large installation area to a display device, such as LCD and CRT display, in a portable electronic device.
It is a further object of the invention to provide a portable electronic device that is equipped with a speaker and a display that can have a large installation area commonly.
According to the invention, a piezoelectric diaphragm, comprises:
a transparent piezoelectric member and a transparent electrode.
According to another aspect of the invention, a piezoelectric diaphragm, comprises:
a first transparent piezoelectric film;
a transparent electrode; and
a second transparent piezoelectric film;
wherein the piezoelectric diaphragm has a lamination structure in which the first transparent piezoelectric film, the transparent electrode and the second transparent piezoelectric film are laminated.
According to another aspect of the invention, a piezoelectric speaker, comprises:
a piezoelectric diaphragm which is composed of a transparent piezoelectric member and a transparent electrode;
a first frame which holds the fringe of the piezoelectric diaphragm on the side of transparent electrode; and
a second frame which holds the fringe of the piezoelectric diaphragm on the side of transparent piezoelectric member;
wherein the first and second frames are installed so that an image to be displayed by a display means is seen through transparent parts inside the first and second frames.
According to another aspect of the invention, a piezoelectric speaker, comprises:
a piezoelectric diaphragm which has a lamination structure in which a first transparent piezoelectric film, a transparent electrode and a second transparent piezoelectric film;
a first frame which holds the fringe of the piezoelectric diaphragm on the side of the first transparent piezoelectric film of the piezoelectric diaphragm; and
a second frame which holds the fringe of the piezoelectric diaphragm on the side of the second transparent piezoelectric film of the piezoelectric diaphragm;
wherein the first and second frames are installed so that an image to be displayed by a display means is seen through transparent parts inside the first and second frames.
According to another aspect of the invention, a portable electronic device, comprises:
a display means to display an image; and
a piezoelectric speaker composed of a transparent piezoelectric member and a transparent electrode;
wherein the piezoelectric speaker is disposed in front of the display means.